Read about pn junction | 21 Discussions | Page 1

  1. T

    Fundamentals of the PN Junction

    Unbiased circuit (no driving voltage source) ************** Fig 1 The N-type material has a tendency to donate electrons to the P-type (i.e. absorb holes from) across the PN junction via diffusion current exclusively within the conduction band of both materials. It does so after those...
  2. Praveen1901

    B P-N junction Semiconductors

    I'm new to semiconductors. While I was studying types of biasing in semiconductors, here's what I read - 'In forward biasing, the width of the depletion region is reduced.' Here's what I thought - Since the potential barrier is reduced in the junction due to external potential, the diffusion...
  3. Muhammad Usman

    I Physics behind P-N Junctions?

    I was reading the PN junction. During the formation of PN junction diffusion process takes place in which the free electrons cross the boundary of the P-N and joined with the holes in the P-type to form the negative ion and holes on the N side cause positive ions. So, the P-side has negative...
  4. Wrichik Basu

    B Do carriers move across a p-n junction at 0 K?

    Often a band diagram is used to explain what happens when two pieces of the same semiconductor, one p-doped, one n-doped, are put together. I am a little confused about it, so here is my question. Initially and at ##0\mathrm{K}##, the surplus carriers should be confined to their respective...
  5. G

    I Relationship between the depletion region and the band gap of a diode?

    Hi, Lately I've been reading about a lab exercise in which Planck's constant is estimated using LEDs. Every procedure I've encountered states that the energy of an emitted photon (and by extension the potential across the semiconductor's band gap) is equal to the threshold voltage multiplied by...
  6. E

    I Concentration of R-G centers in a PN junction

    Hey guys, Currently taking a semiconductor device fundamentals course and we are learning about R-G currents in the depletion region of a PN junction. Usually we just consider R-G centers as impurities to be avoided in the operation of a standard rectifying diode. However, I was curious as to...
  7. T

    B Forward Bias: Why does width of depletion layer decrease?

    The depletion layer is formed by the movement of electrons from the n to p side and holes from p to n side of the diode. The layer consists of positively charged donor ions close to the n side and negatively charged acceptor ions close to the p side. When in equilibrium,the barrier potential...
  8. E

    I Double heterostructure junction in forward and zero bias

    Hi! When dealing with a pn homojunction, it is easy to see the features it has at equilibrium, and also the features it has with forward/reverse bias. Plots show the constant Fermi level at equilibrium and the different Fermi levels for a forward bias; moreover, examples show how much the bands...
  9. E

    I Built-in potential in pn junction

    Hello! The (potential) energy of an electron in a solid structure is always negative; also the E_c and E_v levels (conduction band and valence band limits) are negative, in the band diagram of a pn junction. When the junction is built and thermal equilibrium is reached, the depletion region...
  10. E

    I Diffusion of carriers in a double heterostructure

    Hello! Double heterostructures are used in LEDs and lasers to provide both the confinement of the charge carriers and the confinement of the generated light. This image is a comparison between a homojunction and a heterojunction. As regards the unbiased junctions, when the n region and the p...
  11. E

    I Pn junction to reach thermal equilibrium

    Hello! Some of the processes caused by a pn junction are not clear for me. Just after the contact between the p and the n region, a migration of charges happens in a semiconductor junction in order to reach an equilibrium condition. A valence band and a conduction band are present in both...
  12. G

    Depletion zone and current in forward-biased PN junction

    Hello. I've learned that in PN junction, forward-biasing on it pushes holes in P-type and electrons in N-type toward the junction so depletion width is reduced. Is it due to that in N-type side(P-type side), pushed electrons (holes) are recombined with holes (electrons) in depletion zone? And...
  13. G

    Depletion zone and current in forward-biased PN junction

    Hello. I've learned that in PN junction, forward-biasing pushes holes in P-type and electrons in N-type forward junctions so depletion width is reduced. Is it due to that in N-type (P-type), pushed electrons (holes) are recombined with holes (electrons) in depletion zone? And what is true...
  14. D

    Question about pn diodes and their lifetime

    I was wondering, does the lifetime of a diode depend on how long it takes for all the free P electrons to transfer over to the p holes? In other words, do the electrons that fall into the p holes ever return to the n side?
  15. Amal Thejus

    Static or Dynamic equlibrium in a PN junction?

    Homework Statement We are considering an UNBIASED junction.[/B] I've read in a textbook that electric field created in the junction STOPS diffusion BUT in the same text its written the drift and diffusion currents cancel each other. 1. Does the diffusion and drift currents occur simulataneously...
  16. Amal Thejus

    How can the neutral regions in a diode have constant potential?

    Homework Statement It is said that the potential in the neutral regions of a PN junction diode is CONSTANT. Homework Equations V=Q/4ΠΣr The Attempt at a Solution It is said in all textbooks to ASSUME that the electric field in the neutral regions as zero. Two aspects confuse me. 1. What...
  17. Amal Thejus

    ACTUAL Variation of Potential inside a diode.

    Homework Statement The figures showing the potential variation inside a PN junction normally shows the potential to be constant in the neutral P and N regions Homework Equations V=Q/4ΠΣr The Attempt at a Solution Since the potential due to the positive and negative charges should also exist...
  18. Amal Thejus

    Why there is NO current in a PN junction under equilibrium

    Homework Statement Its said that there is no Net current in a PN junction under equilibrium as the drift and diffusion currents cancel each other. We are talking about a Step junction at equilibrium. Homework Equations Its just a qualitative analysis. 3. The Attempt at a Solution [/B] The...
  19. Amal Thejus

    Variation of Potential outside a PN junction

    Homework Statement 1. We are considering a step junction at equilibrium(no external voltage applied). 2. The potential variation is shown as negative potential at P region(which is shown as constant) and increasing through the transient region to become positive in the n region. Homework...
  20. H

    Is E-field in pn-junctions changing linearly with bias?

    Hi guys, there are a lot of textbooks and articles describe the electric field in depletion region at thermal equilibium, but very few of them tell what happens to the field under bias. I am wondering if the electric field in the depletion region simply changes linearly with reverse bias? Or if...
  21. N

    Pn junction diode (series combo of voltage source and diode)

    The question is to solve the current through a resistor after a pn junction. (photo attached) As far as I'm aware the voltage source in the pn junction is (in this orientation) of opposite polarity to that of the 0.8V voltage source. From my understanding the answer goes like: V=IR I=V/R...
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